<template>
  <ul class="list">
    <li
      v-for="itme of letters"
      :key="itme" @click="handleLetterClick"
      @touchstart="handleTouchStart"
      @touchmove="handleTouchMove"
      @touchend="handleTouchEnd"
      :ref="itme"
    >
    {{ itme }}</li>
  </ul>
</template>

<script>
export default {
  name: 'CityAiphabet',
  props: {
    cities: Object
  },
  computed: {
    letters () {
      const letters = []
      for (let i in this.cities) {
        letters.push(i)
      }
      return letters
    }
  },
  data () {
    return {
      touchStatus: false
    }
  },
  methods: {
    handleLetterClick (e) {
      this.$emit('change', e.target.innerText)
    },
    handleTouchStart () {
      this.touchStatus = true
    },
    handleTouchMove (e) {
      if (this.touchStatus) {
        const startY = this.$refs['A'][0].offsetTop
        const touchY = e.touches[0].clientY - 79
        const index = Math.floor((touchY - startY) / 20)
        if (index >= 0 && index < this.letters.length) {
          this.$emit('change', this.letters[index])
        }
      }
    },
    handleTouchEnd () {
      this.touchStatus = false
    }
  }
}
</script>

<style lang="stylus" scoped>
@import '~styles/varibles.styl'
.list{
  display:flex;
  flex-direction:column;
  justify-content:center;
  position:absolute;
  top:1.58rem;
  right:0;
  width:0.4rem;
  bottom:0;
}
.list li{
  text-align:center;
  line-height:0.44rem;
  color:$bgColor
}
</style>
